China has unveiled the international Cislunar CubeSat Constellation, or C3, project, which plans to deploy 30 small satellites in the space between Earth and the Moon by 2030. They will simultaneously observe different regions of cislunar space, monitor space weather, detect gamma-ray bursts, and collect data needed for future research and lunar exploration.

The program was announced during the 2026 International Conference on Deep Space Exploration, held on September 3–4 in Hefei, China. The project was initiated by the Chinese Deep Space Exploration Laboratory together with the International Deep Space Exploration Association, with support from the Asia-Pacific Space Cooperation Organization.

The constellation will consist of 30 12U-format spacecraft, each weighing no more than 30 kilograms. They are planned to be launched in six batches into elongated Earth–Moon resonant orbits with a 1:3 ratio. Along these trajectories, the satellites will move away from Earth toward the Moon and use the gravitational interaction between the two bodies to maintain stable motion.

This will allow individual small spacecraft to be transformed into a distributed scientific network. Instead of taking measurements at only one location, several satellites will be able to simultaneously record changes in different regions of space and track how particles, magnetic disturbances, and other phenomena propagate between Earth and the Moon.

The lack of such simultaneous measurements remains one of the challenges in studying cislunar space. Chinese specialists note that a significant portion of current data is obtained through individual observations separated in time, whereas C3 is intended to provide continuous network-based monitoring.

Within the project, cislunar space is considered to extend from low Earth orbits to approximately two million kilometers from Earth.

One of the constellation’s tasks is related to space weather. The satellites will measure high-energy particle fluxes and magnetic-field parameters, allowing researchers to simultaneously observe the propagation of disturbances caused by solar activity.

Such data will be particularly important for future crewed missions to the Moon, since intense particle fluxes can pose a risk to astronauts and spacecraft electronics.

China is developing three standard types of scientific instruments for the program: high-energy particle detection systems, space magnetometers, and gamma-ray burst detectors. These instruments are planned to be provided free of charge to international partners.

Participants will also be able to propose their own payloads, while the program provides for joint instrument development and the exchange of scientific data.

The study of gamma-ray bursts — short and extremely powerful emissions of gamma radiation associated with some of the most energetic processes in the Universe — will have a special role.

When the same burst is detected by several spacecraft located far apart from one another, the difference in the signal’s arrival time can be used to determine the direction of its source more accurately.